Intelligent Cooling Fan - Patent 6725132

1. Technical FieldThe present invention relates to cooling fans. More particularly, the present invention relates to intelligent cooling fans for use in electronic systems and for designing cooling solutions for electronic systems.2. Discussion of the Related ArtIn electronic systems, such as computer systems, cooling fans play an important role in maintaining their operational capabilities. The inability to remove excessive heat from electronic systems may lead to permanent damage of the system. Because of the complexity of existing electronic systems, cooling fans having added functionalities other than just providing cooling air, such as the ability to control the speed of a fan, the ability to monitor a tachometer pulse on a fan to determineinstantaneous fan speed, and the ability to detect if a fan has failed or is slower than its preset speed, are required. Although these functionalities exist in some cooling fans today, there is no standard design or protocol that is available tocontrol cooling fans produced by different manufacturers. Moreover, in order to implement these cooling fans within a system, specialized printed circuit assemblies (PCAs), also called controller cards, are required to be designed so as to providesignals that a fan can understand and also to receive and provide signals to the system in a form that is interpretable by the electronics of the system.If one desires additional functionality, such as the ability for the fans to compensate for other failed fans by increasing in speed, the ability for fans to notify external hardware that there is a problem, or the ability for fans to increasespeed in response to increased system temperatures, a specialized PCA or controller card is also required. The PCA or controller card is designed and built to be capable of detecting a fan failure, notifying the system that a fan has failed, andadjusting the speeds of the other fans in the system. The design and manufacture of PCAs and controller

United States Patent: 6725132
&nbsp;
( 1 of 1 )
United States Patent
6,725,132
Frankel
, &nbsp; et al.
April 20, 2004
Intelligent cooling fan
Abstract
A cooling fan including a fan module, a microcontroller, and a bus
interface. The microcontroller is coupled to the fan module and is capable
of adjusting a speed of the cooling fan based on a status of a second
cooling fan and adjusting the speed of the cooling fan based on a
temperature detected. The bus interface is in communication with the
microcontroller, the second cooling fan, and the system to receive and
output data.
Inventors:
Frankel; Scott (Gilbert, AZ), Martin; Peter (Gilbert, AZ), Hardt; Eric (Gilbert, AZ)
Assignee:
Minebea Co., Ltd.
(Tokyo,
JP)
Appl. No.:
10/175,875
Filed:
June 20, 2002
Current U.S. Class:
700/300 ; 361/695; 417/2; 700/70; 702/132
Current International Class:
G05D 23/19&nbsp(20060101); G05D 023/00&nbsp(); G05B 009/02&nbsp(); H05K 007/20&nbsp()
Field of Search:
700/299,300,70 417/2,3 361/690,695 207/130,132
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Other References
US. patent application Publication No. US 2001/0044782 A1.
.
U.S. patent application Publication No. US 2001/0047494 A1..
Primary Examiner: Picard; Leo
Assistant Examiner: Lee; Douglas S.
Attorney, Agent or Firm: Pillsbury Winthrop LLP
Claims
What is claimed is:
1. An electronic system, comprising: a first cooling fan having a first fan module, a first microcontroller coupled to the first fan module, and a first bus interface in
communication with the first microcontroller; and a second cooling fan having a second fan module, a second microcontroller coupled to the second fan module, and a second bus interface in communication with the second microcontroller, wherein the first
microcontroller is capable of adjusting a speed of the first cooling fan based on a status of the second cooling fan, and adjusting the speed of the first cooling fan based on a temperature detected, the first bus interface is in further communication
with the second cooling fan and a system to receive and output data, the second microcontroller is capable of adjusting a speed of the second cooling fan based on a status of the first cooling fan, and adjusting the speed of the second cooling fan based
on the temperature detected, and the second bus interface is in further communication with the first cooling fan and the system to receive and output data.
2. The electronic system according to claim 1, wherein the first microcontroller is further capable of notifying the system of a condition of at least one of the first cooling fan and the second cooling fan.
3. The electronic system according to claim 1, wherein the second microcontroller is further capable of notifying the system of a condition of at least one of the first cooling fan and the second cooling fan.
4. The electronic system according to claim 1, wherein the electronic system further includes a temperature sensor to detect the temperature.
5. The electronic system according to claim 2, wherein the condition is a failure of at least one of the cooling fan and the second cooling fan.
6. The electronic system according to claim 3, wherein the condition is a failure of at least one of the cooling fan and the second cooling fan.
7. The electronic system according to claim 1, wherein the first fan module includes a fan and a motor rotatably coupled to the fan to drive the fan.
8. The electronic system according to claim 1, wherein the second fan module includes a fan and a motor rotatably coupled to the fan to drive the fan.
9. The electronic system according to claim 1, wherein the first bus interface is an Inter-IC (12C) bus interface.
10. The electronic system according to claim 1, wherein the first bus interface includes a data line and a clock line.
11. The electronic system according to claim 1, wherein the second bus interface is an Inter-IC (12C) bus interface.
12. The electronic system according to claim 1, wherein the second bus interface includes a data line and a clock line.
13. The electronic system according to claim 1, wherein the status of the second cooling fan is a fan speed.
14. The electronic system according to claim 1, wherein the status of the first cooling fan is a fan speed.
15. An electronic system, comprising: a first cooling fan having a first fan module, a first microcontroller coupled to the first fan module, and a first Inter-IC (12C) bus interface in communication with the first microcontroller; and a second
cooling fan having a second fan module, a second microcontroller coupled to the second fan module, a second Inter-IC (12C) bus interface in communication with the second microcontroller, wherein the first microcontroller is capable of adjusting a speed
of the first cooling fan based on a status of the second cooling fan, notifying a system of a condition of at least one of the first cooling fan and the second cooling fan, and adjusting the speed of the first cooling fan based on a temperature detected,
the first Inter-IC (12C) bus interface is in further communication with the second cooling fan and the system to receive and output data, the second microcontroller is capable of adjusting a speed of the second cooling fan based on a status of the first
cooling fan, notifying the system of the condition of at least one of the first cooling fan and the second cooling fan, and adjusting the speed of the second cooling fan based on the temperature detected, and the second Inter-IC (12C) bus interface is in
further communication with the first cooling fan and the system to receive an output data.
16. The electronic system according to claim 15, wherein the electronic system further includes a temperature sensor to detect the temperature.
17. The electronic system according to claim 15, wherein the condition is a failure of at least one of the cooling fan and the second cooling fan.
18. The electronic system according to claim 15, wherein the first fan module includes a fan and a motor rotatably coupled to the fan to drive the fan.
19. The electronic system according to claim 15, wherein the second fan module includes a fan and a motor rotatably coupled to the fan to drive the fan.
20. The electronic system according to claim 15, wherein the first Inter-IC (12C) bus interface includes a data line and a clock line.
21. The electronic system according to claim 15, wherein the second Inter-IC (12C) bus interface includes a data line and a clock line.
22. The electronic system according to claim 15, wherein the status of the second cooling fan is a fan speed.
23. The electronic system according to claim 15, wherein the status of the first cooling fan is a fan speed. Description
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to cooling fans. More particularly, the present invention relates to intelligent cooling fans for use in electronic systems and for designing cooling solutions for electronic systems.
2. Discussion of the Related Art
In electronic systems, such as computer systems, cooling fans play an important role in maintaining their operational capabilities. The inability to remove excessive heat from electronic systems may lead to permanent damage of the system.
Because of the complexity of existing electronic systems, cooling fans having added functionalities other than just providing cooling air, such as the ability to control the speed of a fan, the ability to monitor a tachometer pulse on a fan to determine
instantaneous fan speed, and the ability to detect if a fan has failed or is slower than its preset speed, are required. Although these functionalities exist in some cooling fans today, there is no standard design or protocol that is available to
control cooling fans produced by different manufacturers. Moreover, in order to implement these cooling fans within a system, specialized printed circuit assemblies (PCAs), also called controller cards, are required to be designed so as to provide
signals that a fan can understand and also to receive and provide signals to the system in a form that is interpretable by the electronics of the system.
If one desires additional functionality, such as the ability for the fans to compensate for other failed fans by increasing in speed, the ability for fans to notify external hardware that there is a problem, or the ability for fans to increase
speed in response to increased system temperatures, a specialized PCA or controller card is also required. The PCA or controller card is designed and built to be capable of detecting a fan failure, notifying the system that a fan has failed, and
adjusting the speeds of the other fans in the system. The design and manufacture of PCAs and controller cards involve a great deal of engineering time and resources, which ultimately add to the cost of the overall system utilizing the cooling fan(s).
Designing cooling solutions for new systems is also a time-consuming process for the thermal design engineer. Typically, the PCA or controller card is required to be designed and built for controlling the fan speed and other functionality, such
as failure detection and alarm settings. Often times, the design and construction of multiple control cards are required so as to test them in real world applications to obtain the right combination of fans, fan speeds, alarm settings, etc. The multiple
iterations of installing sample fans in a system, determining the adequate fan speeds and power required, and testing the fans in the system, for example, are costly and inefficient.
Another concern involving conventional cooling fans, and in particular, direct current (DC) brushless cooling fans, is that they change speeds depending on the applied input voltage. As the input voltage is increased, the fans speed up and use
more power. When input voltage is decreased, the fans decrease in speed and provide less cooling. Many typical applications have a voltage range that may vary between 24 to 74 volts. Accordingly, a system designer is charged with maintaining a
constant cooling during these wide voltage swings. Accordingly, a voltage regulating power supply is usually installed in a system to keep the voltage to the fans constant. However, having to install a voltage regulating power supply adds additional
complexity and cost to the overall system as well.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a cooling fan solution according to an embodiment of the present invention;
FIG. 2 illustrates an electronic system implementing a plurality of cooling fans according to an embodiment of the present invention;
FIGS. 3A and 3B illustrate a schematic circuit diagram for a cooling fan according to an embodiment of the present invention;
FIG. 4A illustrates voltage and current waveforms according to the prior art;
FIG. 4B illustrates a voltage waveform and a current waveform according to an embodiment of the present invention;
FIG. 4C illustrates a flow chart diagram of a logic path for a microcontroller to maintain a speed of a cooling fan according to an embodiment of the present invention;
FIG. 5 illustrates a sample screen of a fan controller user interface according to an embodiment of the present invention;
FIG. 6 illustrates a sample screen of advanced functions of a fan controller user interface according to an embodiment of the present invention;
FIG. 7 illustrates a flow chart diagram of a logic path for a cooling fan according to an embodiment of the present invention; and
FIG. 8 illustrates a flow chart diagram of determining cooling solution specifications for an electronic system using a cooling fan according to an embodiment of the present invention.
DETAILED DESCRIPTION
FIG. 1 illustrates a cooling fan solution according to an embodiment of the present invention. The cooling fan 100 includes a fan module 110, which has a fan 112 (including fan blades) and a motor 114 rotatably coupled to the fan 112 to drive
the fan 112. A microcontroller 120, such as an 18-pin PIC16C717 microcontroller device manufactured by Microchip Technology, Inc., is in direct communication with the fan module 110, and specifically, the motor 114. Any suitable microcontroller or
processor may be utilized, though. The microcontroller 120 is preferably fixed internally within the cooling fan 100.
A bus interface, such as the Inter-IC (12C) ("12C-Bus Specification", Version 2.1, January 2000, from Philips Semiconductors) bus interface 130 is in communication with the microcontroller 120. The bus interface 130 facilitates transfer of data
to and from the microcontroller 120. The bus interface 130 may be interconnected by bus lines 132, such as 12C bus lines, to a system 140. The 12C bus lines 132 has two lines: a data (SDA) line and a clock (SCL) line. Inter-IC (12C) may be accessed
serially so that each individual device utilizing the 12C protocol has a specific identification (ID), but may all be connected to the same communication line(s) or bus(es) (i.e., it may be connected as a parallel bus). Inter-IC (12C) is a useful
protocol because it is familiar to thermal design engineers who utilize cooling fans in their system designs, and a fair number of digital logic devices utilize the 12C protocol. However, any other bus interface systems and protocols may also be
utilized. For example, the Controller-Area Network (CAN) protocol (Controller-Area Network (CAN) Specification, version 2.0, 1991, Robert Bosch GmbH, Stuttgart, Germany), utilized in the automotive industry, may also be utilized with the bus interface
130 according to an embodiment of the present invention.
Besides the ability for a fan customer or thermal design engineer to control the fan speed, monitor a tachometer pulse on the fan to determine instantaneous fan speed, and detect if the fan has failed or is slower than a preset speed, additional
functionality, such as the ability to electronically read the part number of a cooling fan 100, the ability to electronically determine the fan manufacturer, and the ability to electronically read the manufacturing date, is particularly desirable.
Because of the concern that various fan manufacturers may have different methods of controlling fan speed, or providing alarm or tachometer signals, being able to easily obtain cooling fan 100 information such as the part number, the fan manufacturer,
and the manufacturing date quickly aids in the design and repair of a cooling solution.
According to an embodiment of the present invention, the microcontroller 120 is programmed with program code that enables the microcontroller 120 to read byte communications provided by a system or device 140 that utilizes, for example, the 12C
protocol. In a particular embodiment of the present invention, the microcontroller 120 includes a program memory into which the program code is stored. The PIC16C717 microcontroller, for example, is capable of handling 14-bit words and has a capacity
of 2 kilobytes. The program or instruction code is programmed only once into the microcontroller 120 at the factory, and it is not re-programmable or re-writeable by an end user or cooling fan customer. The PIC16C717 microcontroller, for example, also
includes a small data memory, or "scratch pad memory", having a capacity of 256 bytes available to the microcontroller 120 to conduct its operations. The data memory of the microcontroller 120 is volatile and does not store any programming or
instructions, but rather it is only a working memory.
The program code (such as code written in the "C" programming language) in the microcontroller 120 may include the cooling fan's 100 part number, manufacturer, and date of manufacture so that when the microcontroller 120 receives a command, e.g.,
from the host system/device 140, to output such data to a system or device 140 connected thereto, the microcontroller 120 may readily output the requested data. Useful data other than the cooling fan's 100 part number, manufacturer, and date of
manufacture, such as the current (Amps) draw of the fan, may be included as well. The microcontroller 120 may communicate data regarding the cooling fan 100 in, for example, the 12C protocol. By providing a cooling fan 100 that is capable of directly
communicating with a system or device 140 utilizing a common protocol, such as the 12C protocol, PCAs or controller cards are not required at all to control or communicate with the cooling fan 100.
FIG. 2 illustrates an electronic system implementing a plurality of cooling fans according to an embodiment of the present invention. A plurality of cooling fans 242, 244, 246, 248 are provided within the electronic system 200. Each of the
plurality of cooling fans 242, 244, 246, 248 are electrically connected to a connector module 230, which is a line splitter for a power source 210 and a user system/device 140. According to an embodiment of the present invention, the electronic system
200 utilizes the 12C protocol, and the user system/device 140 has communication lines according to the 12C protocol, a data line 222 and a clock line 224 connected to the connector module 230. The connector module 230 in turn splits the data line 222
and the clock line 224 to each one of the plurality of cooling fans 242, 244, 246, 248. Similarly, the power source lines, power line 212 and power return line 214, from the power source 210 are connected to the connector module 230, which in turn
splits the power line 212 and the power return line 214 to each one of the plurality of cooling fans 242, 244, 246, 248.
Specific addresses required in all 12C devices may be set externally (by connecting address lines high for a "1", or low for a "0"), or internally during production. The data line 222 and the clock line 224 for each one of the plurality of
cooling fans 242, 244, 246, 248 and the user system/device 140 may be connected to each other, or to an internal bus, which enables the user system/device 140, for example, to change the fan speeds of any one of the plurality of cooling fans 242, 244,
246, 248, to detect the fan speeds of any one the plurality of cooling fans 242, 244, 246, 248, to read the part number of any one the plurality of cooling fans 242, 244, 246, 248, etc.
According to another embodiment of the present invention, the microcontroller 120 may be programmed with a program code to enable each cooling fan 100 to detect failures of other cooling fans 242, 244, 246, 248 to notify a user system/device 140
that a fan has failed, or to adjust the speeds of the other fans in the system to compensate. In the prior art, a specialized PCA or controller card was required to be designed and built to provide these functionalities for an electronic system 200
utilizing cooling fans 242, 244, 246, 248. Accordingly, the microcontroller 120 may be programmed with program code so that each cooling fan 242, 244, 246, 248 has the ability to detect and compensate for other failed fans by increasing its fan speed,
to notify external hardware 140 that there is a problem, or to increase its fan speed in response to increased system temperatures. By having each of the plurality of cooling fans 242, 244, 246, 248 in communication with each other, added redundancy and
functionality may be provided to the overall system 200.
In one particular embodiment, the cooling fans 242, 244, 246, 248 are connected to each other by their communication lines 132 (see FIG. 1), which may be facilitated by a connection to a shared bus. If one of the cooling fans 242, 244, 246, 248
fails, then the failure is detected by the other cooling fans 242, 244, 246, 248. Upon this failure detection, the other cooling fans 242, 244, 246, 248 may be programmed to increase the fan speed to compensate for the decreased airflow due to the
failure of one of the cooling fans 242, 244, 246, 248. In a further embodiment, temperature sensors may be implemented utilizing the 12C protocol and connected to the plurality of cooling fans 242, 244, 246, 248 so that each of the cooling fans 242,
244, 246, 248 may communicate directly with the temperature sensors (or through the host system/device 140 if the temperature sensors are not directly connected to the cooling fans 242, 244, 246, 248). Therefore, the plurality of cooling fans 242, 244,
246, 248 may be further programmed to increase fan speeds if an increase in temperature is detected by the temperature sensors, or decrease the fan speed if the temperature drops. In other words, the cooling fans 242, 244, 246, 248 may also be aware of
the temperatures detected by the temperature sensors installed within the system and act accordingly. By connecting the cooling fans 242, 244, 246, 248 to each other and placing them into a "multi-master" mode, each cooling fan 242, 244, 246, 248 is in
communication with each other and the redundant and failure recovery operations discussed above may be implemented.
By implementing a microcontroller 120 and a bus interface 130 utilizing a standard protocol, such as the 12C protocol, engineers are freed from designing and building a PCA or controller card, the resulting system is not burdened with the
additional cost of the controller card, and the cooling fan 100 may be directly added to the existing bus of the customer or design engineer hardware. The cooling fans 242, 244, 246, 248 (see FIG. 2) may be connected to each other, or to a commonly
connected printed circuit board (PCB), to greatly simplify cooling solution design and construction. Moreover, the savings of not requiring a specialized PCA or controller card are significant, as they may run three times the cost of the cooling fan
itself. In one particular embodiment, the cooling fans 242, 244, 246, 248 may be compatible with, for example, the IBM Specification 18P3640 (October 2001) Type 5 fans.
According to yet another embodiment of the present invention, a cooling fan 100 (see FIG. 1) is provided that is capable of operating at a constant speed even with changing/varying input voltage and/or motor load. As mentioned above, the
majority of conventional DC brushless cooling fans change speeds with applied input voltage. As the input voltage is increased, the fans speed up and use more power. When input voltage is decreased, the fans decrease in speed and provide less cooling.
Many existing applications have a voltage range that can vary from 24 to 74 volts. The design engineer is charged with maintaining a constant cooling for the system during these wide voltage swings. Typically, the design engineer installs a voltage
regulating power supply in the system to keep the voltage to the fans constant. However, providing a voltage regulating power supply adds more complexity and increases the cost to the overall system.
FIGS. 3A and 3B illustrate a schematic circuit diagram for a cooling fan according to an embodiment of the present invention. In an embodiment according to the present invention, the microcontroller 120 has program code having instructions to
detect the speed of the cooling fan 100 in real time and maintain that speed, regardless of changes in the input voltage. Referring to FIG. 3A, line E1 312 is the voltage (in) line, while line E2 314 is the voltage return (ground). In a preferred
embodiment of the present invention, lines 322 and 324 are Inter-IC (12C) lines: line 322 being the data line and line 324 being the clock line for communication utilizing the 12C protocol. Typically, in cooling fan applications, the input voltage may
be 12 volts, 24 volts, or 48 volts. Diodes D1 and D2 332 provide for reverse polarity protection within the system. Zenor diode D5 334 provides a drop in power and regulates the voltage to, for example, 12 volts. A 5V regulator 342 is included to
provide regulated 5 volts to the microcontroller 120 and the speed sensor 116 (e.g., the Hall sensor). The Hall sensor 116 provides a digital signal to the microcontroller 120 based on the positions of the stator 380 of the fan motor 114 utilizing the
Hall effect, which occurs when the charge carriers moving through a material experience a deflection because of an applied magnetic field. This deflection results in a measurable potential difference across the side of the material which is transverse
to the magnetic field and the current direction. According to one embodiment, the Hall sensor 116 provides a 50% duty cycle signal, that is, two pulses for each revolution/cycle of the fan. Based on the signals provided by the Hall sensor 116, the
microcontroller 120 is capable of determining the speed of the cooling fan 100 and making any adjustments necessary to maintain a constant fan speed.
Referring to FIG. 3B, the microcontroller 120 is connected to two metal-oxide semiconductor field effect transistor (MOSFET) drivers 350, 360. Through the MOSFET drivers 350, 360, the microcontroller 120 controls the duty cycle (on time vs. off
time) of the voltage provided to the fan motor 114, and more specifically, to the MOSFETs 372, 374, 376, 378 and across the stator 380. According to an embodiment of the present invention, the drains of MOSFETs 372, 376 are coupled to the variable input
voltage (from line E1 312). The gate of MOSFET 372 is coupled to the high (H0) line (7) of MOSFET driver 350. The gate of MOSFET 376 is also coupled to the high (H0) line (7) of MOSFET driver 360. The logic on pin 2, input from the microcontroller
120, of each MOSFET driver 350, 360 are controlled by different lines, lines D and E, respectively. The state of pin 2 is the same as the H0 pin of each MOSFET driver 350, 360, and the microcontroller 120 alternates these signals so that MOSFETs 372,
376 are not in the "high" state at the same time.
The sources of MOSFETs 372, 376 are each coupled to a node to which the drains of each of MOSFETs 374, 378 are respectively coupled, and to which the stator 380 is coupled. The gate of MOSFET 374 is coupled to the low output (L0) line (5) of
MOSFET driver 350. The gate of MOSFET 378 is also coupled to the low output (L0) line (5) of MOSFET driver 360. The sources of each of MOSFETs 374, 378 are coupled to a reference voltage or ground 338. In the configuration illustrated in FIG. 3B,
MOSFETs 372, 378 are "on" at the same time while MOSFETs 374, 376 are "off", and alternatively, when MOSFETs 374, 376 are "on", MOSFETs 372, 378 are "off".
Accordingly, when an increasing speed is detected via the Hall sensor 116, the microcontroller 120 reduces the stator duty cycle to maintain the same energy transfer to the motor windings. The shifts in duty cycle are implemented in program code
embedded within the microcontroller 120. Resistor 336 provides a locked rotor detection signal for the microcontroller 120. The microcontroller 120 detects the current flowing through the windings by monitoring the voltage representation of the current
that appears on resistor 336. If this voltage exceeds a set threshold set internal to the microcontroller 120, then the output pulses are terminated and a locked rotor condition is perceived. The capacitors C1 and C2 338 provide for voltage ripple
filtering and as additional protection to limit high switching currents from causing noise in the user's system.
FIG. 4A illustrates voltage and current waveforms according to the prior art. For example, the nominal voltage for a cooling fan is 48 Vdc. If the voltage is increased to 60 Vdc, for example, the fan has a physical tendency to increase in speed
as a reaction to more voltage and energy being switched by the MOSFETs 372, 374, 376, 378 (see FIG. 3B). The top waveform set 410 represents the voltage across a stator 380 with waveform 414 representing 48 volts and waveform 412 representing 60 volts.
The bottom waveform set 420 represents the current through the stator 380 with waveform 424 representing a 48 volt input and waveform 422 representing a 60 volt input. Accordingly, without taking any additional measures, the increased voltage and
current causes additional energy to be transferred to the coils, which results in a faster spinning fan.
Rather that utilizing a voltage regulating power supply as in the prior art, according to an embodiment of the present invention, the microcontroller 120 of the cooling fan 100 monitors the speed sensor 116, such as a Hall sensor, to detect an
increasing speed. Alternatively, the back electromagnetic field (EMF) generated by an increase in speed of the cooling fan 100 may be monitored to detect the increase in speed as well. To compensate for the increasing speed, the microcontroller 120 has
program code having instructions to reduce the stator duty cycle (i.e., the on-time vs. the off-time) to maintain the same energy transfer to the motor 114 when an increase in speed is detected. Preferably, the fan speed is controlled utilizing Pulse
Width Modulation (PWM), i.e., driving the fan motor 114 using short pulses (the pulses vary in duration to change the speed of the motor--the longer the pulses, the faster the motor turns, and vice versa).
FIG. 4B illustrates a voltage waveform and a current waveform according to an embodiment of the present invention. The top waveform 430 represents a reduced stator duty cycle (on-time vs. off-time) of the voltage (e.g., 60 Vdc) as compared to
waveform 412 in FIG. 3A. The bottom waveform 440 represents a reduced stator duty cycle of the current as compared to waveform 424 in FIG. 3A. Accordingly, while the voltage and current has increased, the "time-on" of each has been decreased to
maintain the same energy transfer to the motor 114, and thereby regulate the fan speed. In one embodiment of the present invention, shifts in the stator duty cycle based on the various voltage levels are preprogrammed in the program code embedded within
the microcontroller 120.
FIG. 4C illustrates a flow chart diagram of a logic path for a microcontroller to maintain a speed of a cooling fan according to an embodiment of the present invention. A reference constant is provided 401 (programmed into the microcontroller
120) corresponding to the constant speed at which the cooling fan 100 is to be maintained. The microcontroller 120 enters a main routine 402 for its normal operation. The program code embedded within the microcontroller 120 determines whether a speed
sensor interrupt, such as a Hall sensor interrupt signal, was generated 403. If such an interrupt was not generated, then the operation flows back to block 402. If an interrupt was generated, then a timer value lapsed since the occurrence of the last
interrupt signal is captured 404. It is determined 405 whether the timer value is greater or less than the reference constant, which represents the desired fan speed. If the timer value is less than the reference constant, then the duty cycle (such as
the PWM duty cycle) is decremented 406 by one clock, the timer is reset 407 for a new comparison, and operation flows back to block 402. If the timer value is greater than the reference constant, then the duty cycle (such as the PWM duty cycle) is
incremented 408 by one, the timer is reset 409 for a new comparison, and operation flows back to block 402. If the timer value is equal to the reference constant, then the operation flows back to block 402.
By utilizing the cooling fan 100 according to an embodiment of the present invention, the thermal design engineer does not need to design and build a specialized power supply or other additional circuitry in a PCA, controller card, or in the fan
tray in order to compensate for the negative effects on cooling due to swings of the system voltage. Moreover, specialized power supplies can easily cost three times that of the fan itself. The cooling fan 100 according to an embodiment of the present
invention provides a constant fan speed regardless of the input voltage, and design time and costs are significantly reduced.
FIG. 5 illustrates a sample screen of a fan controller user interface according to an embodiment of the present invention. The fan controller user interface 500 is preferably a software program executing on a computer system, such as a desktop
personal computer (PC) or a laptop computer. The desktop PC or laptop computer may be connected to a network and accessed remotely via, for example, the Internet using Internet Protocol (IP). The fan controller user interface software 500 enables a
thermal design engineer to quickly create a cooling solution for a specific application. A typical application of the fan controller user interface software 500 is for designing a cooling solution for a new cabinet/housing for an electronic system.
When designing a cooling solution for a new cabinet/housing, the design engineer does not know: (1) how much airflow is needed; (2) what types of alarms are required; (3) what functions are necessary on the controller card circuitry; and (4) how
the system should behave with increasing system temperature. By utilizing the fan controller user interface software 500 according to an embodiment of the present invention, the design engineer may quickly install cooling fans 100 according to
embodiments of the present invention and connect these fans to a computer system (e.g., a desktop PC or a laptop computer) executing the fan controller user interface software 500 to determine the cooling solution specifications for a particular
cabinet/housing.
The cooling fan(s) 100 are connected to a power source and then to the computer system executing the fan controller user interface software 500. The cooling fan(s) 100 may be connected to a fan/computer adapter, which converts the communications
protocol utilized by the cooling fan(s) 100, such as the 12C protocol, to one recognizable by the computer system, such as the Universal Serial Bus (USB) protocol. The fan/computer adapter then plugs into, for example, the USB port on the computer
system so that the computer system is in communication with the cooling fan(s) 100.
After assembling the cooling fan(s) 100 into a system cabinet/housing, the design engineer starts the fan controller user interface software 500. As illustrated in the main screen 500 of FIG. 5, the design engineer may change the speed of any
cooling fan 510, 520, 530, 540 connected, set basic alarms, monitor the temperature sensor(s) connected, and constantly refresh the data of all of the cooling fan(s) 510, 520, 530, 540 (part number, speed, alarm status, etc.). In one embodiment, the
temperature sensor(s) 122 may be incorporated inside the microcontroller 120. The fan controller user interface software 500 emulates the program code resident in a microcontroller 120 to control the behavior of each cooling fan 510, 520, 530, 540. In
other words, the fan controller user interface software 500 is adapted to allow a user to control and operate all of the functions of each cooling fan 510, 520, 530, 540. Therefore, all of the functions of each cooling fan 510, 520, 530, 540 are
available to the thermal design engineer for design troubleshooting and prototyping.
The main screen shot 500 of FIG. 5 shows basic information for four cooling fans 510, 520, 530, 540, including their part numbers, fan identifications, fan speed, and status (e.g., active, stop, etc.). Basic information for two temperature
sensors is also provided, including their sensor identifications, part numbers, and the temperatures detected. Other information may also be provided to the user on the screen. There is provided a fan control entry window 570 that allows a basic speed
of the fans 510, 520, 530, 540 to be set, as well as a basic alarm, for example, to be actuated when the fan speed, revolutions per minute (RPM), drops below a certain level. A message box 580 may also be provided to inform the user of events that occur
during the use of the fan controller user interface software 500. The fan speeds of a plurality of cooling fans within a system may be set slightly different from each other so as to test for and eliminate any beat-frequencies that may occur, which may
cause unwanted noise.
FIG. 6 illustrates a sample screen of advanced functions of a fan controller user interface according to an embodiment of the present invention. In the advanced function screen 610 illustrated in FIG. 6, "what if" conditional scenarios may be
set and tested. For example, a scenario may be configured to design an appropriate response to when one of the cooling fans 510, 520, 530, 540 fails. The advanced function screen 610 allows a design engineer to easily conduct such a scenario and
program and test for an appropriate response. For example, the following logic condition may be set and tested:
If FAN A speed is slower than 1500 RPM then set FAN B to 3500 RPM and TRIP ALARM 1.
The fan controller user interface software 500 may be configured so that the commands are in a straightforward sentence-like structure, allowing the user to manipulate the terms from a menu for the bold-underlined terms above to vary a condition. The above example illustrates a sample condition when one cooling fan (Fan A) that is failing is rotating slower than 1500 RPM, a second cooling fan (Fan B) is adjusted to increase in speed (to 3500 RPM) to provide added cooling to the system, and then
alarm 1 is tripped, which may be preconfigured to alert the user that there is a problem in the system (or even more specifically, that Fan A is failing). A number of other conditional scenarios may configured using the fan controller user interface
software 500 according to an embodiment of the present invention. Moreover, conditional scenarios involving temperature sensors may also be established using a similar methodology. Therefore, the thermal design engineer is able to set and test a
variety of different conditions and program the appropriate behavior for each fan 510, 520, 530, 540 to respond accordingly to each condition.
FIG. 7 illustrates a flow chart diagram of a logic path for a cooling fan according to an embodiment of the present invention. FIG. 7 illustrates a failure detect process from the perspective of Fan A in a system having four fans, Fans A-D.
According to an embodiment of the present invention, each of the Fans A-D have a parallel connection to an Inter-IC (12C) bus. Initially, Fan A sends 710 a status request to Fan B. It is determined whether a response is received 720 by Fan A from Fan B
within a predetermined period of time, e.g., 2 seconds. If a response is received, it is determined whether a failure mode response was received 730. If a failure mode response is not received, Fan A waits for a predetermined period of time, e.g., 5
seconds, then repeats 740 the above iteration with Fan C. If no response is received by Fan A from Fan B within the predetermined period of time (e.g., 2 seconds), or if a failure mode response is received by Fan A from Fan B, then the assumption is that
Fan B has failed (or is failing) and Fan A proceeds to increase 750 its fan speed based on the cooling solution specifications/operating parameters and programming determined using the fan controller user interface software 500, a failure notification
regarding Fan B's failure is transmitted 760 by Fan A, and Fan A waits for a predetermined period of time, e.g., 5 seconds, then repeats 740 the above iteration with Fan C. Once the iteration with Fan C is completed, the iteration is also performed with
respect to Fan D.
FIG. 8 illustrates a flow chart diagram of determining cooling solution specifications for an electronic system using a cooling fan according to an embodiment of the present invention. At least one cooling fan is installed 810 within a housing.
Operating parameters are set 820 for the at least one cooling fan. Operation of the at least one cooling fan within the housing is conducted 830 based on the operating parameters set. The operating parameters of the at least one cooling fan are
captured 840 if the operating parameters result in adequate cooling within the housing by the at least one cooling fan.
Once the user has made the appropriate configurations for the behavior for each fan 510, 520, 530, 540 and is satisfied with the functionality of the fans 510, 520, 530, 540 installed in the cabinet/housing, the user may "freeze" the design and
store the cooling solution specifications or operating parameters determined (e.g., each fan's RPM settings, alarms, conditions, temperature conditions, conditional behaviors (e.g., to compensate for a fan failure, temperature increase), etc., for that
particular cabinet/housing). The cooling solution specifications may be forwarded to a cooling fan manufacturer, and specific cooling fans adhering to the customized cooling solution specifications may be manufactured, including the appropriate
programming desired by the engineer set forth during the testing with the fan controller user interface software 500, and provided to the design engineer, knowing already that the cooling solution utilizing cooling fans with these characteristics and
programming logic have already been tested and proven.
By utilizing the fan controller user interface software 500 according to an embodiment of the present invention, the thermal design engineer saves a significant amount of time in the design cycle by eliminating the need to design and build a
specialized PCA or controller card for controlling the speeds and alarm settings of the cooling fan(s) 510, 520, 530, 540, and eliminating the iteration of asking for a fan sample, trying the fan out in the system, asking for a second higher-powered fan
sample, trying the fan out in the system, etc., to determine a suitable cooling solution for a cabinet/housing. The thermal design engineer is able to balance airflow, noise, redundancy, and temperature response utilizing the fan controller user
interface software 500 without having to go through an iterative process.
While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such
modifications as would fall within the true scope and spirit of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by
the appended claims, rather than the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
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